JP2977595B2 - Syndiotactic polypropylene molded article and method for producing the same - Google Patents

Description

The present invention relates to a syndiotactic polypropylene molded article and a method for producing the same. For more information, molding with high tacticity syndiotactic polypropylene or a copolymer or a mixture of copolymer and isotactic polypropylene with excellent transparency and excellent balance between rigidity and impact resistance And a method of molding the same.

(Prior art)

Syndiotactic polypropylene has been known for a long time, but the conventional method of polymerizing at low temperature with a catalyst comprising a vanadium compound, ether and organoaluminum is said to have poor syndiotacticity and elastomeric properties. However, it was hard to say that it inherently characterizes syndiotactic polypropylene. In contrast, JA
EWEN et al. Discovered for the first time that a catalyst comprising a transition metal compound having an asymmetric ligand and an aluminoxane could produce a polypropylene having good tacticity with a syndiotactic pentad fraction exceeding 0.7 (J. Am. Chem. Soc., 1988, 110, 6255-6256).

[Problems to be solved by the invention]

The molded product of the syndiotactic polypropylene obtained by the above method or a copolymer of propylene having substantially a syndiotactic structure and another olefin has relatively excellent transparency, but its transparency is still insufficient. I couldn't say.

[Means for solving the problem]

The present inventors have solved the above-mentioned problems and have intensively searched for a syndiotactic polypropylene molded article having good transparency, and specific ones are extremely excellent in transparency, and also excellent in balance between rigidity and impact resistance. The inventors have found that the present invention has been completed.

That is, the present invention relates to a propylene homopolymer having a substantially syndiotactic structure, a copolymer with a small amount of another olefin, or a mixture thereof with a small amount of a polypropylene having a substantially isotactic structure. After being heated and melt-formed, by rapid cooling, the melting point attributed to the syndiotactic polypropylene measured at a temperature of 10 ° C./min by differential scanning calorimetry is substantially a single peak. This is a molded article or a syndiotactic polypropylene molded article having good transparency obtained by subsequently subjecting this molded article to a heat treatment at a temperature not higher than the melting point. The present invention is also a preferred method for producing the above-mentioned molded article, comprising a homopolymer of propylene having a substantially syndiotactic structure, a copolymer with a small amount of another olefin, or a small amount thereof with an isotactic. Syndiotactic polypropylene with good transparency, characterized in that a mixture with polypropylene having a structure is heated and melt-molded and then quenched at 100 ° C / min or higher, or heat-treated to a temperature below the melting point following quenching. This is a method for producing a molded article.

In the present invention, a propylene homopolymer having a substantially syndiotactic structure means one having a syndiotactic pentad fraction of 0.5 or more, preferably 0.7 or more, and a small amount of another olefin. With respect to the copolymer with, in its ¹³ C-NMR spectrum, 20.2 pp
The peak intensity observed at m is 0.3 or more, preferably 0.5 or more, of the intensity of all peaks attributed to the methyl group of the propylene unit. The method for calculating the syndiotactic pentad fraction is described in A. Zambelli et al .; Macro
molecules vol.8,687 (1975) and vol.6,925 (197
3), the ¹³ C-NMR spectrum of the polymer
It is obtained by measuring a 1,2,4-trichlorobenzene solution based on tetramethylsilane.

Examples of the catalyst used for producing a propylene homopolymer having a substantially syndiotactic structure or a copolymer with a small amount of another olefin in the present invention include the compounds described in the above-mentioned documents. Even if the catalyst has a structure different from that of the examples, any catalyst system that can produce a polypropylene having a syndiotactic pentad fraction of 0.7 or more when propylene is homopolymerized can be used.

Examples of the transition metal compound having an asymmetric ligand include isopropyl (cyclopentadienyl-1-fluorenyl) hafnium dichloride, isopropyl (cyclopentadienyl-1-fluorenyl) zirconium dichloride, and transition metals described in the above literature. Compounds in which at least one of the chlorine atoms of the compound is substituted with an alkyl group are exemplified. (Wherein R is a hydrocarbon residue having 1 to 3 carbon atoms). In particular, methylaminoxan wherein R is a methyl group and n is 5 or more, preferably 10 to 100 used. The use ratio of the aluminoxane to the transition metal compound is 10 to 100,000,000 mole times, usually 50 to 5000.
It is molar times. The polymerization conditions are not particularly limited, and a solvent polymerization method using an inert medium, a bulk polymer substantially free of an inert medium, and a gas phase polymerization method can be used. Generally, the polymerization is carried out at a temperature of -100 to 200 ° C. and at a pressure of normal pressure to 100 kg / cm ² -G. Preferably, it is -100 to 100 ° C and normal pressure to 50 kg / cm ² -G.

Examples of the other olefin used in the copolymerization include ethylene and α-olefins having 4 to 20 carbon atoms. Specific examples include butene-1, pentene-1, hexene-1, octene-1, and 4-methylpentene. 1 and the like. The ratio of polymerization to propylene is usually 20wt%
The following other olefins are polymerized under copolymerization conditions,
If the amount exceeds wt%, the rigidity of the molded body is undesirably reduced.
The conditions for performing the copolymerization are not particularly limited, and commonly used known conditions can be employed as they are. When the polymerization is carried out in substantially one-stage polymerization, the obtained polymer has a narrow molecular weight distribution and a ratio of the weight average molecular weight to the number average molecular weight measured by gel permeation chromatography at 135 ° C. (hereinafter abbreviated as MW / MN). Is usually 1.5-3.
It is about 5, but two kinds of transition metal compounds (for example, it is effective to use two kinds of metals such as zirconium and hafnium) or a mixture of two or more kinds having different molecular weights. It is possible to produce a product having a wide molecular weight distribution such that MW / MN is 3.5 or more, and it is preferable to use the present invention. Preferred molecular weight is 13
Generally, the intrinsic viscosity (hereinafter abbreviated as η) measured with a 5 ° C. tetralin solution is about 0.5 to 5.0 dl / g. Also part of syndiotactic polypropylene,
For example, up to less than 50% by weight can be replaced by polypropylene having an isotactic structure, whereby a molded article having higher rigidity can be obtained.

The above syndiotactic polypropylene or mixture is then heated and melted and formed into a specific shape. The molding method is not limited as long as it can be cooled rapidly after molding, and an extrusion molding method or an injection molding method can be adopted.

What is important in the present invention is from the molten state of the compact.
Rapid cooling at a rate of 100 ° C./min or more, preferably 150 to 1000 ° C./min. As a method of quenching, it is common to bring a coolant into contact with the molded body, but it can also be carried out by introducing a molten resin into a relatively low-temperature atmosphere. In this way, the compact after quenching can be cooled to 10 ° C by differential scanning calorimetry.
The melting point attributable to the polypropylene having the syndiotactic structure measured by raising the temperature at / min can be substantially a single peak. From the molten state of the compact
When measured by differential scanning calorimetry at the same heating rate for those cooled slowly at a rate of less than 100 ° C./min, this melting point does not appear as a single peak, but as two peaks as shown in FIG. 1 (c). Or more peaks are observed. Moreover, the one thus cooled slowly is not preferable because the transparency is not sufficient as shown in Comparative Examples 1 to 5 described later. Incidentally, the position of the melting point, which is substantially a single peak observed for the quenched product, is once melted at 250 ° C. by ordinary conditions, ie, differential scanning calorimetry, and then at 10 ° C./mi.
The temperature is lowered to 30 ° C with n, and the temperature is raised again at 10 ° C / min. The peak is observed at a lower temperature than the position of the highest peak among the peaks of melting point (2 to 3 observed). Is usually the case.

It is of course possible to utilize a crystallization nucleating agent when quenching after the melt molding.

Although the molded body in this quenched state has extremely excellent transparency, the rigidity is inferior to that of the usual one. Further, by heating the molded body to a temperature equal to or lower than the melting point, the rigidity can be greatly improved without substantially impairing the transparency. The higher the heating temperature, the shorter the time is required, but generally the temperature of about 50 ° C. to the melting point is generally used, and the heating time is several seconds to several hours, and the relatively high temperature is more effective in a shorter time. . The standard is about 100 ° C to several hours.

〔Example〕

 Hereinafter, the present invention will be described with reference to Examples.

Example 1 0.2 g of isopropyl (cyclopentadienyl-1-fluorenyl) zirconium dichloride obtained by lithiation of isopropylcyclopentadienyl-1-fluorene synthesized according to a conventional method, reaction with zirconium tetrachloride and recrystallization. And 30 g of methylaluminoxane manufactured by Toyo Akzo Co., Ltd. (degree of polymerization 16.1) were added to toluene 80 in an autoclave having a volume of 200, and propylene was polymerized at a polymerization pressure of 3 k
Polymerization was performed at g / cm ² -G at 20 ° C. for 2 hours to obtain a polymer.
The polymer was demineralized with methanol and methyl acetoacetate, washed with an aqueous hydrochloric acid solution, and then filtered to obtain 5.6 kg of Shinsotatactic polypropylene. According to ¹³ C-NMR, the polypropylene had a syndiotactic pentad fraction of 0.935, and η measured at 135 ° C. in a tetralin solution was 1.
MW / MN measured at 45 dl / g, 1,2,4-trichlorobenzene is
2.2. A known stabilizer was added to this polypropylene, granulated with an extruder, and then melt-pressed at 200 ° C. to obtain 1 mm
And quenched in water at 0 ° C. During this quenching, the temperature drop rate was measured by a sensor inserted at the center of the sheet and found to be 250 ° C./min. The following physical properties of this sheet were measured.

・ Bending stiffness: kg / cm ² ASTM D-747 (23 ° C) ・ Tensile yield strength: kg / cm ² ASTM D-638 (23 ° C) ・ Elongation at break:% ASTM D-638 (23 ° C) Izod (with notch) impact strength: kg · cm / cm ASTM D-638 (23 ° C, -10 ° C) Haze:% According to ASTM D1003.

Flexural rigidity, tensile yield strength, elongation at break, Izod impact strength (23 ° C, -10 ° C) are 5800, 240, 507,
It was 45, 3.6 and the haze was 21. FIG. 1 (a) shows the melting behavior measured at 10 ° C./min by differential scanning calorimetry. The melting point attributed to the syndiotactic structure is substantially a single peak. ing.

This sheet is further placed in an electric furnace controlled at 145 ° C. for 30 minutes.
After heat treatment for minutes, the physical properties of the sheet are as follows, and the tensile yield strength and the bending rigidity are improved. The flexural rigidity, tensile yield strength, elongation at break, and Izod impact strength (23 ° C., −10 ° C.) were 6,800, 280, 43, 45, 3.4, respectively, and the haze was 24. In addition, differential scanning calorimetry
FIG. 1 (b) shows the melting behavior measured at a temperature rise of 10 ° C./min.

Comparative Example 1 In Example 1, except that the press sheet was cooled under a normal condition, that is, cooled at 80 ° C./min by cooling in a state where the press sheet was formed, the physical properties were measured in the same manner. Degree, tensile yield strength, elongation at break, Izod impact strength (23 ° C, -10 ° C) are 6200, 26
The haze was 56, 1,520, 12.7, 3.6. FIG. 1 (c) shows the melting behavior by the differential scanning calorimetry measured under the same conditions as in Example 1.

This sheet was subjected to a heat treatment at 145 ° C. for 30 minutes and its physical properties were measured. The flexural rigidity was 6400, the tensile yield strength was 265,
Elongation at break 180, Izod impact strength (23 ℃, -10 ℃)
Were 12.7 and 3.4, and the physical properties were slightly improved by the heat treatment, but the haze was 61, which was poor.

Example 2 A copolymer having a hexene content of 6% by weight was obtained in the same manner as in Example 1 except that hexene-1 was used in the polymerization. This copolymer has a peak intensity observed at 20.2 ppm according to ¹³ C-NMR of 0.75 with respect to the sum of the intensities of all peaks attributed to the methyl group of the propylene unit, and is therefore substantially syndiotactic. It was of a structure. The physical properties of the sheet obtained by heating and melt-molding the copolymer in the same manner as in Example 1 and then quenching were measured, and the flexural rigidity, tensile yield strength, elongation at break, and Izod impact strength (23 ° C., − 10 ℃) is 4800, 200, 633, 45, 3.8 respectively
And the haze was 15. Further, the melting point attributed to the polypropylene having a syndiotactic structure, measured by differential scanning calorimetry at a temperature rise of 10 ° C./min, was substantially a single peak. When this sheet was heated at 110 ° C for 60 minutes, the flexural rigidity, tensile yield strength, elongation at break, and Izod impact strength (23 ° C, -10 ° C) were each 51.
00, 230, 520, 45, 3.2 and the haze was 18.

Comparative Example 2 In Example 2, the press sheet was cooled under normal conditions, that is, cooled at 85 ° C./min by cooling while forming the press sheet. Temperature, tensile yield strength, elongation at break, and Izod impact strength (23 ° C, -10 ° C) are 5000 and 21 respectively.
0, 585, 13.5, 3.7, and haze was 47.

Example 3 Isopropylcyclopentadienyl-1-fluorene synthesized according to a conventional method was lithiated, reacted with hafnium tetrachloride (containing 5 wt% zirconium), and recrystallized to obtain isopropyl (cyclopentadienyl). 0.1 g of -1-fluorenyl) hafnium dichloride and 0.1 g of isopropyl (cyclopentadienyl-1-fluorenyl) zirconium dichloride synthesized in Example 1;
Methylaluminoxane manufactured by Toso-Akzo Co., Ltd.
6.1) 30 g of toluene 8 in an autoclave with an internal volume of 200
In addition to 0, propylene was polymerized at 20 ° C. for 2 hours at a polymerization pressure of 3 kg / cm ² -G to obtain a polymer. The polymer was deashed with methanol and methyl acetoacetate, washed with an aqueous hydrochloric acid solution, and then filtered to obtain 4.6 kg of syndiotactic polypropylene. The syndiotactic pentad fraction of this polypropylene is 0.904, η is 1.68 dl / g, MW /
MN was 5.2. Example 1 using this polypropylene
Similarly, granulate with an extruder and melt-press at 200 ° C to 1mm
And quenched in water at 0 ° C. During this quenching, the high-temperature rate was measured by a sensor inserted at the center of the sheet and found to be 250 ° C./min. Bending stiffness,
Tensile yield strength, elongation at break, Izod impact strength (23
C, -10C) were 5200, 210, 480, 45, and 3.8, respectively, and the haze was 8.5. 10 ° C / differential scanning calorimetry
The melting point attributable to the syndiotactic polypropylene measured in min was a substantially single peak at 135.3 ° C. The sheet was further placed in an electric furnace controlled at 130 ° C. and heat-treated for 30 minutes. The properties of the sheet were as follows, and the tensile yield strength and the bending rigidity were improved. Flexural rigidity, tensile yield strength, elongation at break, Izod impact strength (23 ° C, -10 ° C) are 5800, 245, 43, 45, respectively.
3.8 and the haze was 10.3.

Comparative Example 3 In Example 3, the press sheet was cooled under normal conditions, that is, cooled at 80 ° C./min by cooling in a state where the press sheet was formed. Degree, tensile yield strength, elongation at break, Izod impact strength (23 ° C, -10 ° C) are 5250, 21
The values were 0, 420, 12.7, and 3.6, and the haze was 58.

Example 4 A copolymer having a hexene content of 6% by weight was obtained in the same manner as in Example 3 except that hexene-1 was used in the polymerization. This copolymer has a peak intensity observed at 20.2 ppm according to ¹³ C-NMR of 0.68 with respect to the sum of the intensities of all peaks attributed to the methyl group of the propylene unit, and is therefore substantially syndiotactic. It was of a structure. Also, MW / MN
It was 4.5. The physical properties of the sheet obtained by heating and melt-molding the copolymer in the same manner as in Example 3 and then quenching were measured. The sheet was measured for flexural rigidity, tensile yield strength, elongation at break, Izod impact strength (23 ° C., -10 ℃)
They were 4600, 190, 640, 45 and 3.8, and the haze was 16. Further, the melting point attributed to the polypropylene having a syndiotactic structure, which was measured by raising the temperature at 10 ° C./min by differential scanning calorimetry, was substantially a single peak. This sheet was further placed in an electric furnace controlled at 110 ° C. and subjected to heat treatment for 60 minutes, whereupon the bending stiffness, tensile yield strength, elongation at break,
Izod impact strength (23 ℃, -10 ℃) is 5100,
240, 490, 45, 3.3 and the haze was 17.

Comparative Example 4 In Example 4, the press sheet was cooled under normal conditions, that is, cooled at 85 ° C./min by cooling in a state where the press sheet was formed. Degree, tensile yield strength, elongation at break, Izod impact strength (23 ° C, -10 ° C) are 5100, 22
They were 0, 460, 18.5, 3.7 and the haze was 44.

Example 5 Syndiotactic polypropylene 90 obtained in Example 3
To the parts by weight, a commercially available isotactic polypropylene (isotactic pentad fraction 0.962, η is 1.62 dl /
g) 10 parts by weight were mixed. The MW / MN of the mixture was 7.5. This mixture was heated and melt-molded in the same manner as in Example 1 and then rapidly cooled to form a sheet-like molded body. When physical properties of this sheet were measured, flexural rigidity, tensile yield strength, elongation at break, and Izod impact strength (23 ° C, -10
C) were 6,800, 260, 150, 14.5, and 3.0, respectively, and the haze was 24. The melting point was measured with a differential scanning calorimeter in the same manner as in Example 3. As a result, the melting point attributed to the syndiotactic polypropylene was a substantially single peak at 145.5 ° C. The assigned melting point was 162.0 ° C. This sheet is further placed in an electric furnace controlled at 145 ° C.
After heat treatment for 0 minutes, the physical properties of the sheet are as follows, and the tensile yield strength and the bending rigidity are improved. Flexural rigidity, tensile yield strength, elongation at break, Izod impact strength (23 ° C, -10 ° C) are 7900, 295, 45, 15.4,
3.1 and haze was 25.

Comparative Example 5 In Example 5, except that the press sheet was cooled under a normal condition, that is, cooled at 80 ° C./min by cooling in a state where the press sheet was formed, the physical properties were measured in the same manner. Degree, tensile yield strength, elongation at break, Izod impact strength (23 ° C, -10 ° C) are 7300 and 26, respectively.
8, 64, 13.3, 2.8 and the haze was 75.

〔The invention's effect〕

The molded article of the present invention has extremely good transparency and excellent balance of physical properties, and therefore is extremely valuable industrially particularly for use as a film or sheet.

[Brief description of the drawings]

FIG. 1 shows the melting behavior of the polymer obtained by analyzing the molded products of Example 1 and Comparative Example 1 by differential scanning calorimetry, and FIG.
Corresponds to before the heat treatment of Example 1, (b) corresponds to after the heat treatment of Example 1, and (c) corresponds to Comparative Example 1.

──────────────────────────────────────────────────の Continuing on the front page (51) Int.Cl. ⁶ Identification code FI C08L 23:10 (31) Priority claim number Japanese Patent Application No. 2-11800 (32) Priority date Hei 2 (1990) January 23 ( 33) Priority country Japan (JP) (58) Fields studied (Int. Cl. ⁶ , DB name) C08J 5/00 B29C 35/00 B29C 71/02

Claims (8)

(57) [Claims] 1. Hot melt molding of a homopolymer of propylene having a substantially syndiotactic structure, a copolymer with a small amount of another olefin, or a mixture thereof with a small amount of polypropylene having an isotactic structure. And then quenched by differential scanning calorimetry.
A highly transparent syndiotactic polypropylene molded article having a substantially single peak melting point attributable to a syndiotactic polypropylene measured at a temperature rise of 10 ° C./min. 2. Hot melt molding of a homopolymer of propylene having a substantially syndiotactic structure, a copolymer with a small amount of another olefin, or a mixture thereof with a small amount of a polypropylene having an isotactic structure. And then quenching at 100 ° C./min or more. A method for producing a syndiotactic polypropylene molded article having good transparency. 3. A propylene homopolymer having a substantially syndiotactic structure, a copolymer with a small amount of another olefin, or a mixture thereof with a small amount of a polypropylene having a substantially isotactic structure. After heating and melt-molding, by quenching, the melting point attributed to polypropylene having a syndiotactic structure measured at a temperature of 10 ° C./min by differential scanning calorimetry is substantially a single peak. A syndiotactic polypropylene molded article having good transparency, which is formed into a molded article and then subjected to a heat treatment at a temperature not higher than the melting point. 4. A propylene homopolymer having a substantially syndiotactic structure, a copolymer with a small amount of another olefin or a mixture thereof with a small amount of a polypropylene having a substantially isotactic structure. A method for producing a syndiotactic polypropylene molded article having good transparency, characterized by quenching at 100 ° C./min or more after heat-melt molding, and then heat-treating to a temperature below the melting point. 5. A propylene homopolymer having a substantially syndiotactic structure or a copolymer with a small amount of another olefin, wherein the ratio of the weight average molecular weight to the number average molecular weight is 1.5 to 3.5. After heating and melt-molding the polymer, it is rapidly cooled, and the melting point measured at 10 ° C./min by differential scanning calorimetry is substantially a single peak. body. 6. A homopolymer of propylene having a substantially syndiotactic structure or a copolymer with a small amount of another olefin, wherein the ratio of the weight average molecular weight to the number average molecular weight is 1.5 to 3.5. 100 ° C /
A method for producing a syndiotactic polypropylene molded article having good transparency, characterized by quenching at a rate of at least min. 7. A homopolymer of propylene having a substantially syndiotactic structure or a copolymer with a small amount of another olefin, wherein the ratio of the weight average molecular weight to the number average molecular weight is 1.5 to 3.5. After heating and melt-molding the polymer, it is quenched to obtain a differential scanning calorimetry of 10 ° C / min.
A molded article having a melting point substantially equal to a single peak by raising the temperature, and then subjected to a heat treatment at a temperature not higher than the melting point to obtain a syndiotactic polypropylene molded article having good transparency. 8. A homopolymer of propylene having a substantially syndiotactic structure or a copolymer with a small amount of another olefin, wherein the ratio of the weight average molecular weight to the number average molecular weight is 1.5 to 3.5. 100 after heat melting and molding the polymer
A method for producing a syndiotactic polypropylene molded article having good transparency, characterized by quenching at a temperature of at least ℃ / min and then heat-treating to a temperature below the melting point.